Process for treating mineral oils



Patented Aug. 22, 1939 PATENT OFFICE 2,170,620 v rnocsss ron. TREATINGMINERAL OILS Constantin Skrepinsky,

Elizabeth, N. J., assignor to Standard Oil Development Company, acorporation of Delaware No Drawing. Application December 24, 1936,Serial No. 117,537

7 Claims.

This invention relates to a process of treating mineral oils and refersparticularly to a process of producing improved lubricating oils frommineral 011 stocks heavier than kerosene.

In the refining of lubricating oils, especially light coloredlubricating oils, such as white oils' which are used for medicinalpurposes, the oils are generally submitted to very drastic treatments.It has been found in the past that the 10 more drastic treatments towhich these lubricating stocks are submitted, the more unstable is thefinished oil. These oils which have been treated in this manner onstanding, especially in sunlight, very quickly deteriorate and formacidic 1 compounds, which are noticeable by the presence of a pronouncedodor. Onv the other hand, if a lubricating oil stock is only subjectedto a mild treatment, for example, with a small amount of sulufuric acid,the resulting oil is more stable to oxidation, but upon being used, morereadily forms a sludge deposit.

An object of the invention is to provide a process whereby a stablelubricating oil may be prepared. Another object of this invention is toprovide an improved method for preparing lubrieating oils, especiallystable white oils that are used for medicinal purposes and will meet therequirements of the U. S. Pharmacopoeia.

According to this invention, it has been found 0 that by treating apetroleum lubricating oil distillate fraction with oxygen oroxygen-containing gas without the aid of solid absorbents and addedsteam for 3 or 4 hours, the non-stable hydrocarbon constituents dooxidize and polymerize. The

85 temperatures used for the oxidation are from 400 to 500 F. The lowertemperatures of about 400 F. are used when lubricating oil fractions oflow viscosity are being treated, that is, those of -S. A. E. 10 to 20,and the higher temperature of 40 about 450 to 500 F. being used for oilsof higher viscosity such as S. A. E. to 50. The quantity of air or anyoxygen-containing gas used is from about 5 to 7 cubic feet per hour forevery 300 grams of the oil. Catalysts such as copper naphthenate,manganese stearate, etc., may be used to aid the oxidation.

The oxidized oil is then treated with a small quantity of about 1% to 5%of concentrated sulfuric acid to coagulate theoxidized compounds whichare then separated as a sludge. If it is desired to prepare a mineralwhite oil that will meet the requirements of U. S. Pharmacopoeia, theoxidized oil is treated with approximately 15 5 to 30% by weight offuming sulfuric acid after which the oil may be clay filtered, to thedesired color.

By this method, smaller amounts of acid are required to prepare a.mineral white 011, that is, the amount of fuming sulfuric acid requiredto produce a white mineral oil suitable for medicinal purposes isreduced from to 80% or more to 15' to 30%. Also, the mineral white oilthereby prepared is more stable and has a lower oxygen absorption ratethan that'prepared by acid treatment followed by clay filtration to thesame color.

Where the oil is to be used only for lubricating purposes, such as in aninternal combustion engine, 1 to 5% of concentrated sulfuric acidisqgenerally suflicient to remove any of the oxidized constituents thathave been formed. This oil may then be clay treated to improve the coloror such. This oil is especially adapted for use as a turbine oil,transformer oil, motor oil, or in any other manner where a lubricatingoil is required that will withstand oxidation over long periods of time.It has also been observed that by this treatment the viscosity index israised, the pour lowered, Sligh number improved, and

the finished oil generally improved.

The oil being treated may be subjected to preliminary treatments beforebeing oxidized, that is, the asphaltic constituents may be separated bypropane separation, or it may be subjected to an acid treatment toeliminate any unsaturated or aromatic compounds that may be present. Itlikewise may be subjected to treatments with selective solvents toremove unsaturated and aromatic compounds. A finished oil may beimproved and made more stable by beingsubjected to this treatment. It isnot necessary that an oil treated according to this method be treatedwith clay as the oxidized constituents are readily coagulated by the useof the small quantity of acid, after which the oil may be neutralizedand washed. Selective solvents, such as phenol furfural, sulfur dioxide,etc. may also be used to finish up the oil.

The advantages obtained by this process will be more clearly understoodon the reading of the following examples:

Emample 1 A distillate obtained from a Columbia crude mineral oil,having a medium viscosity of about S. A. E. 30 and a pour point of 0 F.after being oxidized by blowing with 5 to 7 cubicv feet of air per hourper 300 grams of the oilfor 3 to 4 hours at a temperature of about 450F., was subjected to the following treatment: 1 to 3% concentratedsulfuric acid was added to coagulate and separate the oxidizedconstituents and the separated oil filtered through clay (1 ton of clayper 100 barrels of oil). The pour point of this finished oil was reducedto -20 F. and the viscosity index of the finished oil was increased 3 to4 Example 2 points.

the pour point of the finished product was reduced to -10 F.

Example 3 A lubricating oil distillate obtained from a Columbia crudeand having a Saybolt viscosity of 700 seconds at 100 F. was blown withto '7 cubic feet of air per hour for every 300 grams of the oil at atemperature of about 400' to 450 F. for 2%; to 4 hours. The oil then wassubjected to three treatments each of 5% by volume of fuming" sulfuricacid, after which it was neutralized after; being separated from thesludge, washed with al.-- cohol and filtered'through clay (1 ton ofclayper 60 barrels of oil). The oxidation absorp: tion rate of the oilwas 15 cc. of oxygen per minutes for every grams of the oil, ata.temiperature of 175 0., whereas the usual whiteoilsz on the markethave oxygen absorption rates. of over 100, generally in the neighborhoodof 14102110. 160. The oil also passed the U. S. Pharmacopoeia. acidtest.

The oxygen absorption rate was determined; by circulating a known volumeof oxygen through; 10 grams of the oil at a temperature of 1.75: C. fora period of minutes and the amount of oxygen absorbed by the oil is theabsorption. rate: of. the said 011'.

Example 4 A distillate obtained from a Columbia crude having a Saybolt'viscosity of 574- seconds at 100 F. and 59 seconds at 210 F; and with'adetails which may have been given merely for illustrative purposes, butis limited only in and by the following claims in which all the noveltyinherent in the invention is claimed.

1 claim:

1. The method of treating hydrocarbon oils to produce a stable.lubricating oil which comprises treating the lubricating oil distillatewith a gas containing'free oxygen of about'5 to 7 cubic feet of the saidgas for every 300 grams of the oil per our at a temperature of about400-450 F. for a period of. about 3 to 4 hours, treating the saidoxidized oil with 1 to 30% sulfuric acid and separating the acid sludgethat is formed.

2.. The; method of treating hydrocarbon oils according to claim 1 inwhich an oxidizing catalyst is used.

3... The method of treating hydrocarbon oils according to claim 1 inwhich the separated oil istreated with clay to obtain a light color.

4. The method of treating a hydrocarbon oil to: produce a mineral whiteoil that is suitable for medicinal purposes which comprises contactingat a temperature of about 400-45031. a lubricating oil fraction for 3 to4 hours with 5 cubic feet of a gas containing free oxygen for 300 gramsof the said oil, contacting the said oxidized oil with of fumingsulfuric acid by weight, separating the acid sludge that formed andfiltering the separated oil through a. body of absorbent clay.

5. The method of treating a hydrocarbon oil to produce a minerallubricating oil which comprises contacting at a temperature of about460-450" F. a lubricating'oil fraction for 3 to 4 hours with 5 cubicfeet of a gas containing free oxygen for every 300 grams of .the said.oil ,v contacting the said oxidized oil with l to-3-% of con centratedsulfuric acid by weight and separating the acid sludge that is formed.

6. The method of treating a hydrocarbon oil to produce a mineral whiteoil that is: suitable for medicinal purposes and passing; the U. S.Pharmacopoeia acid test, which comprises contacting at a temperature ofabout 400-450 F. a lubricating oil distillate for 3 to 4 hours with 5cubic feet. of a gas containing free oxygen for every 300 grams of thesaid oil, subjecting said oxidized oil to 3 treatments of 5% each offuming sulfuric acid by weight, separating the acid sludge as it isformed and filtering the separated oil through a body of absorbent clay.

'7. The method of treating a hydrocarbon oil to produce a mineral whiteoil according to claim 6 in which the treated oil, after being separatedfrom the sludge, is neutralized and washed with alcohol before filteringthrough clay.

